Disubstituted Maleic Anhydrides with Altered Kinetics of Ring Closure

ABSTRACT

We describe anhydride compounds suitable for physiologically labile modification of amine-containing molecules. The described anhydrides form reversible linkages having desirable kinetics for in vivo delivery of biologically active molecules. Also described are endosomolytic polymers formed by modification of membrane active polyamines with the described anhydrides.

BACKGROUND OF THE INVENTION

Maleic anhydrides are used in medicinal and formulation chemistry forlabile covalent linkage between molecules of interest. Introduction ofalkyl substituents at positions 2 and 3 of maleic anhydride shiftsequilibrium of reaction with aliphatic amines towards free amine andmaleic anhydride at pH<7.

At pH>7, the reaction is driven toward the maleamate (maleamic acid whencarboxyl group is protonated). At acidic pH, the reaction is driventowards the anhydride and the free amine. This property is usefulbecause in mammals, the pH of blood is about 7.4 (slightly alkaline)while certain intracellular compartments, such as endosomes andlysosome, are acidic (pH<6).

The rate of conversion of maleamates to amines and maleic anhydrides isstrongly dependent on substitution at positions 2 and 3 (R1 and R2) ofthe maleic anhydride system. When R1 and R2 are both hydrogen (maleicanhydride) the reaction is nearly irreversible. Substitution of a singlealkyl group at position R1 or R2 (e.g., citraconic anhydride) increasesthe rate of the reverse reaction 50-fold higher compared to maleicanhydride. At pH 5, the half life for cleavage of a mono-substitutedmaleamate to yield the free amine and the anhydride is about 8 to 24 h.This half-life is too slow for delivery systems where rapid lability isimportant. For disubstituted maleamates, steric repulsion of the 2,3aliphatic groups drives the reaction toward ring closure to form theanhydride and free amine (Kirby Adv. Phys. Org. Chem. 1980, 17, 183-278;Kirby et al. J Chem Soc., Perkin Trans. 2, 1972, 1206-1214). Alkylsubstitutions at both R1 and R2 (e.g., 2,3-dimethylmaleic anhydride)increase the rate of the reverse reaction 10,000-fold compared to maleicanhydride. Half-life of cleavage of a disubstituted maleamate from apolyamine is about 5 min at 37° C. and pH 5.5.

The reverse reaction for 2-propionic-3-methylmaleamic acid has beenobserved to be the same as that for 2,3-dimethylmaleamic acid. We havepreviously described the use of 2-propionic-3-methylmaleic anhydride(CDM) derivatives for reversible modification of amine-containingpolymers (Rozema et al. Proc. Natl. Acad. Sci. USA, 2007, Vol. 104, No.32, p. 12982-12966). However, the half-life for dialkyl-substitutedmaleamates can be too energetically favorable, i.e. amide cleavage canoccur too rapidly even near neutral pH, for certain in vivo labiledelivery systems. At pH 7.5 and 37° C., cleavage of the amide bond in2,3-dialkyl maleamates to yield anhydrides and free amines occurs with at_(1/2) of about 4 h. This rate is too rapid for applications in whichlonger circulation time is desired. Thus, there is a need forphysiologically labile bonds which are more stable in circulation yetretain rapid reversibility in the pH 6 environment of a cell endosome.

It has been shown that connecting alkyl substitutions into a cycledecreases the rate of ring closure reaction in 2,3-dialkyl maleamate.For example, amine release from mono N-methylamido derivative formedfrom 4,5,6,7-terahydrobenzo[c]furan-1,3-dione and methylamine hask_(obs)=3.5×10⁻² (Kirby Adv. Phys. Org. Chem. 1980, 17, 183-278), is17.5 times faster than for respective 2-methylmaleamate and 32 timesslower than for 2,3-dimethylmaleamate. For benzo[c]furan-1,3-dione,introduction of alkyl groups at positions 4 and 7 shifts equilibrium inwater toward ring closure. K=k₁/k⁻¹ in this equilibrium is 1.5, comparewith K=5.3 for the same equilibrium measured for dimethyl maleic acid,or K=10² for phthalic acid itself (Eberson et al. J. Am. Chem. Soc.1971, Vol. 93, No. 22, p. 5821-5826).

We describe here new disubstituted maleic anhydrides which yieldmaleamates having half-lives that are shorter than mono-substitutedmaleamates but slower than previously described dialkyl-substitutedmaleamates. These new anhydrides, with their slower rate of amidecleavage, achieve longer circulation times in vivo and extended shelflife relative to formulations using previously described disubstitutedmaleic anhydrides.

SUMMARY OF THE INVENTION

In a preferred embodiment, we describe a class of maleic anhydridederivatives having a cyclohexene or benzene ring fused to the c-side ofthe maleic anhydride (2,5-furandione) ring: benzo[c]furan-1,3-diones(phthalic acid anhydrides) and cyclohexene[c]furan-1,3-diones.

In one embodiment, we describe modified cyclohexene[c]furan-1,3-diones,CycHex-CDM, having the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and    -   n is an integer from 0-8; and,        R1, R2, and R3 are independently selected from hydrogen,        aliphatic group, and aromatic group.

In one embodiment, we describe membrane active polyamines reversiblymodified by reaction with the above described CycHex-CDM, having thestructure:

wherein X, R1, R2, and R3 are as described above. In a preferredembodiment, X comprises a targeting group. A preferred targeting groupis an N-acetylgalactosamine. In another preferred embodiment, Xcomprises a steric stabilizer. A preferred steric stabilizer is apolyethyleneglycol (PEG). In yet another preferred embodiment, aplurality of maleic anhydrides of the invention are linked to a singlepolyamine. In yet another preferred embodiment, the reversibly modifiedmembrane active polyamine in not membrane active. Cleavage of theanhydrides from the modified polymer, such as in response to a decreasein pH, restores amines, and thereby membrane activity, to the membraneactive polyamine.

In another embodiment, we describe 4,7-disubstitutedbenzo[c]furan-1,3-dione (Benzo-CDM), having the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and    -   n is an integer from 0-8; and,        R1, R2, and R3 are independently selected from hydrogen,        aliphatic group, and aromatic group, and m is an integer from        1-8.

In one embodiment, we describe membrane active polyamines reversiblymodified by reaction with the above described Benzo-CDM having thestructure:

wherein X, R1, R2, R3, and m are as described above. In a preferredembodiment, X comprises a targeting group. A preferred targeting groupis an N-acetylgalactosamine. In another preferred embodiment, Xcomprises a steric stabilizer. A preferred steric stabilizer is a PEG.In yet another preferred embodiment, a plurality of maleic anhydrides ofthe invention are linked to a single polyamine. In yet another preferredembodiment, the reversibly modified membrane active polyamine is notmembrane active. Cleavage of the anhydrides from the modified polymer,such as in response to a decrease in pH, restores amines, and therebymembrane activity, to the membrane active polyamine.

In a preferred embodiment, we describe disubstituted maleic anhydridesin which one of the substitutions contains an electron withdrawing group(EWG). Electron withdrawing groups draw electrons away from a reactioncenter. By placing an electron withdrawing group at position C2 or C3 ofthe anhydride, the pKa of the anhydride constituent carboxylic acid isreduced. Thus, introduction of electron withdrawing groups (EWG) intomaleamates increases acidity of the carboxyl group thereby decreasingthe rate of the ring closure reaction.

In one embodiment, we describe 4-Ar-furan-1,3-dione derivatives (Ar-CDM)having the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and n is an integer from        0-8; and,        R1 is an aliphatic group or aromatic group.

In one embodiment, we describe membrane active polyamines reversiblymodified by reaction with the above described Ar-CDM, having thestructure:

wherein X and R1 are as described above. In a preferred embodiment, Xcomprises a targeting group. A preferred targeting group is anN-acetylgalactosamine. In another preferred embodiment, X comprises asteric stabilizer. A preferred steric stabilizer is a PEG. In yetanother preferred embodiment, a plurality of maleic anhydrides of theinvention are linked to a single polyamine. In yet another preferredembodiment, the reversibly modified membrane active polyamine is notmembrane active. Cleavage of the anhydrides from the modified polymer,such as in response to a decrease in pH, restores amines, and therebymembrane activity, to the membrane active polyamine.

In another embodiment, we describe 4-alkoxy-furan-1,3-dione derivatives(Alkoxy-CDM) having the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and    -   n is an integer 0-8;

Y is —CH₂—O—R1 or —NH—CO—R1; and

R1 is an aliphatic group.

In one embodiment, we describe membrane active polyamines reversiblymodified by reaction with the above described Alkoxy-CDM, having thestructure:

wherein X, M, and Y are as described above. In a preferred embodiment, Xcomprises a targeting group. A preferred targeting group is anN-acetylgalactosamine. In another preferred embodiment, X comprises asteric stabilizer. A preferred steric stabilizer is a PEG. In yetanother preferred embodiment, a plurality of maleic anhydrides of theinvention are linked to a single polyamine. In yet another preferredembodiment, the reversibly modified membrane active polyamine is notmembrane active. Cleavage of the anhydrides from the modified polymer,such as in response to a decrease in pH, restores amines, and therebymembrane activity, to the membrane active polyamine.

In another embodiment, we describe 4-alkoxy-furan-1,3-dione derivatives(Alkoxy-CDM) having the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a hydroxyl group or Z may comprise a targeting group as        defined herein or a steric stabilizer group as defined herein,        and    -   n is an integer 0-8;        R1 is an aliphatic group.

In one embodiment, we describe membrane active polyamines reversiblymodified by reaction with the above described Alkoxy-CDM, having thestructure:

wherein X, and R1 are as described above. In a preferred embodiment, Xcomprises a targeting group. A preferred targeting group is anN-acetylgalactosamine. In another preferred embodiment, X comprises asteric stabilizer. A preferred steric stabilizer is a PEG. In yetanother preferred embodiment, a plurality of maleic anhydrides of theinvention are linked to a single polyamine. In yet another preferredembodiment, the reversibly modified membrane active polyamine is notmembrane active. Cleavage of the anhydrides from the modified polymer,such as in response to a decrease in pH, restores amines, and therebymembrane activity, to the membrane active polyamine.

The disubstituted maleic anhydrides described above may be use toreversibly link a molecule of interest to an amine containing compound.The molecule of interest may be at position R1, R2, R3, or Z of any ofthe above described anhydrides. The molecule of interest may be selectedfrom the group comprising: active pharmaceutical ingredient (API), smallmolecule drug, nucleic acid, interaction modifier, targeting group, ordelivery agent. Preferably, the molecule of interest does not itselfcontain a free amine.

In another preferred embodiment, the invention features a compositionfor delivering a polynucleotide to a cell in vivo comprising areversibly modified membrane active polymer as described abovereversibly conjugated to a polynucleotide via a physiologically labilelinkage. The physiologically labile linkage to the polynucleotide may becleaved under the same or different conditions than the maleamatelinkages. The polynucleotide-polymer conjugate is administered to amammal in a pharmaceutically acceptable carrier or diluent.

Further objects, features, and advantages of the invention will beapparent from the following detailed description when taken inconjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compounds, compositions, andmethods useful for reversibly modifying membrane active polymers. Thereversibly modified polymers are suitable for delivering polynucleotidesor other cell-impermeable molecules to mammalian cells. The compoundscomprise disubstituted maleic anhydride derivatives having desirablekinetics of ring closure in physiological conditions. As shown in thereaction above, anhydrides are able to react with anime groups inaqueous solution in a reaction that is reversible. Reaction of adisubstituted maleic anhydride derivative with an amine yields amaleamate. The maleamate is pH labile. At acidic pH, the maleamate amidebond is cleaved, yielding a cyclic anhydride and the amine Thus,disubstituted maleic anhydride derivatives provide a means to reversiblylink a molecule of interest, such as a small molecule, targeting group,steric stabilizer, or nucleic acid to an amine-containing compound, suchas a membrane active polyamine, via a physiologically labile linkage.

CycHex-CDM compounds of the invention have the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and n is an integer from        0-8; and,        R1, R2, and R3 are independently selected from hydrogen,        aliphatic group, and aromatic group.        Z is selected to contain a molecule of interest, such as a        targeting group or a steric stabilizer, or to be a reactive        group which can be used to attach the molecule of interest.

Benzo-CDM compounds of the invention have the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and n is an integer from        0-8; and,        R1, R2, and R3 are independently selected from hydrogen,        aliphatic group and aromatic group, and m is an integer from        1-8.        Z is selected to contain a molecule of interest, such as a        targeting group or a steric stabilizer, or to be a reactive        group which can be used to attach the molecule of interest.

Ar-CDM compounds of the invention have the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and n is an integer 0-8;        and,        R1 is an aliphatic group or aromatic group.        Z is selected to contain a molecule of interest, such as a        targeting group or a steric stabilizer, or to be a reactive        group which can be used to attach the molecule of interest.

Alkoxy-CDM compounds of the invention have the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is carboxyl group, ester group, amide group, ether group,        tertiary amine group, or protected amine group, or Z may        comprise a targeting group as defined herein or a steric        stabilizer group as defined herein, and n is an integer 0-8;

Y is —CH₂—O—R1 or —NH—CO—R1; and

-   -   R1 is an aliphatic group.        Z is selected to contain a molecule of interest, such as a        targeting group or a steric stabilizer, or to be a reactive        group which can be use to attach the molecule of interest.

Amido-CDM compounds of the invention have the structure:

wherein X is —(CH₂)_(n)—Z,

-   -   Z is a hydroxyl group or Z may comprise a targeting group as        defined herein or a steric stabilizer group as defined herein,        and    -   n is an integer 0-8;        R1 is an aliphatic group.        Z is selected to contain a molecule of interest, such as a        targeting group or a steric stabilizer, or to be a reactive        group which can be use to attach the molecule of interest.

Each of the above compounds, CycHex-CDM, Benzo-CDM, Ar-CDM, andAlkoxy-CDM react with amines to yield physiologically labile maleamatelinkages. In particular, the compounds of the invention are particularlysuitable for reversible modification of membrane active polymers asdescribed in U.S. Patent Publications 2008-0152661 and U.S. patentapplication Ser. No. 13/032,029 (each of which is incorporated herein byreference)

A linkage or linker is a connection between two atoms that links onechemical group or segment of interest to another chemical group orsegment of interest via one or more covalent bonds. For example, alinkage can connect a molecule of interest to a polymer. A reversible orlabile linkage contains a reversible or labile bond. A linkage mayoptionally include a spacer that increases the distance between the twojoined atoms. A spacer may further add flexibility and/or length to thelinkage. Spacers may include, but are not be limited to, alkyl groups,alkenyl groups, alkynyl groups, aryl groups, aralkyl groups, aralkenylgroups, aralkenyl groups; each of which can contain one or moreheteroatoms, heterocycles, amino acids, nucleotides, and saccharides.Spacer groups are well known in the art and the preceding list is notmeant to limit the scope of the invention.

A labile bond is a covalent bond other than a covalent bond to ahydrogen atom that is capable of being selectively broken or cleavedunder conditions that will not break or cleave other covalent bonds inthe same molecule. More specifically, a labile bond is a covalent bondthat is less stable (thermodynamically) or more rapidly broken(kinetically) under appropriate conditions than other non-labilecovalent bonds in the same molecule. Cleavage of a labile bond within amolecule may result in the formation of two molecules. For those skilledin the art, cleavage or lability of a bond is generally discussed interms of half-life (t_(1/2)) of bond cleavage (the time required forhalf of the bonds to cleave). Thus, reversible or labile bonds encompassbonds that can be selectively cleaved more rapidly than other bonds in amolecule.

Appropriate conditions are determined by the type of labile bond and arewell known in organic chemistry. Labile bonds of maleamates as disclosedherein are pH sensitive. Cleavage of the maleamate linkage isaccelerated in acidic pH.

As used herein, a physiologically labile bond is a labile bond that iscleavable under conditions normally encountered or analogous to thoseencountered within a mammalian body. Physiologically labile linkagegroups are selected such that they undergo a chemical transformation(e.g., cleavage) when present in certain physiological conditions.

As used herein, a cellular physiologically labile bond is a labile bondthat is cleavable under mammalian intracellular conditions. Mammalianintracellular conditions include chemical conditions such as pH,temperature, oxidative or reductive conditions or agents, and saltconcentration found in or analogous to those encountered in mammaliancells. Mammalian intracellular conditions also include the presence ofenzymatic activity normally present in a mammalian cell such as fromproteolytic or hydrolytic enzymes.

Reversible modification of a membrane active polyamine with thedescribed disubstituted maleic anhydride compounds reducesnon-productive serum and non-target cell interactions and reducestoxicity of the polyamine in vivo. Further utility is gained by usingthe described disubstituted maleic anhydride compounds to reversiblyattach targeting ligands and steric stabilizers to the membrane activepolyamines Reversible modification to attach targeting groups and/orsteric stabilizers enhance cell-specific binding and endocytosis, shieldthe polymer from non-specific interactions, increase circulation time,enhance specific interactions, inhibit toxicity, or alter the charge ofthe polymer. The described physiologically labile disubstitutedmaleamates maintain sufficient stability in the pH 7.4 environment ofthe blood, but are readily cleaved from the polyamine, thereby unmaskingthe polyamine and restoring activity of the unmasked polyamine in thereduced pH environment of the cellular endosome/lysosome.

As used herein, membrane active polymers are surface active, amphipathicpolymers that are able to induce one or more of the following effectsupon a biological membrane: an alteration or disruption of the membranethat allows non-membrane permeable molecules to enter a cell or crossthe membrane, pore formation in the membrane, fission of membranes, ordisruption or dissolving of the membrane. As used herein, a membrane, orcell membrane, comprises a lipid bilayer. The alteration or disruptionof the membrane can be functionally defined by the polymer's activity inat least one the following assays: red blood cell lysis (hemolysis),liposome leakage, liposome fusion, cell fusion, cell lysis, andendosomal release. Membrane active polymers that can cause lysis of cellmembranes are also termed membrane lytic polymers. Polymers thatpreferentially cause disruption of endosomes or lysosomes over plasmamembrane are considered endosomolytic. The effect of membrane activepolymers on a cell membrane may be transient. Membrane active polymerspossess affinity for the membrane and cause a denaturation ordeformation of bilayer structures. Membrane active polymers may besynthetic or non-natural amphipathic polymers.

As used herein, membrane active polymers are distinct from a class ofpolymers termed cell penetrating peptides or polymers represented bycompounds such as the arginine-rich peptide derived from the HIV TATprotein, the antennapedia peptide, VP22 peptide, transportan,arginine-rich artificial peptides, small guanidinium-rich artificialpolymers and the like. While cell penetrating compounds appear totransport some molecules across a membrane, from one side of a lipidbilayer to other side of the lipid bilayer, apparently without requiringendocytosis and without disturbing the integrity of the membrane, theirmechanism is not understood.

Delivery of a polynucleotide to a cell is mediated by the membraneactive polymer disrupting or destabilizing the plasma membrane or aninternal vesicle membrane (such as an endosome or lysosome), includingforming a pore in the membrane, or disrupting endosomal or lysosomalvesicles thereby permitting release of the contents of the vesicle intothe cell cytoplasm.

Endosomolytic polymers are polymers that, in response to anendosomal-specific environmental factor, such as reduced pH or thepresence of lytic enzymes, are able to cause disruption or lysis of anendosome or provide for release of a normally cell membrane impermeablecompound, such as a polynucleotide or protein, from a cellular internalmembrane-enclosed vesicle, such as an endosome or lysosome.Endosomolytic polymers undergo a shift in their physico-chemicalproperties in the endosome. This shift can be a change in the polymer'ssolubility or ability to interact with other compounds or membranes as aresult of a shift in charge, hydrophobicity, or hydrophilicity.Exemplary endosomolytic polymers have pH-labile groups or bonds. Areversibly masked membrane active polymer, wherein the masking agentsare attached to the polymer via pH labile bonds, can therefore beconsidered to be an endosomolytic polymer.

Modification of the membrane active polymer can be done to reversiblyinhibit, or mask, the polymer and to provide cell or tissue targetingproperties. Modification using the described anhydrides also neutralizesthe polyamine to reduce positive charge and form a near neutral chargedpolymer.

The membrane active polyamines of the invention are capable ofdisrupting plasma membranes or lysosomal/endocytic membranes. Thismembrane activity is an essential feature for cellular delivery of thepolynucleotide. Unmodified membrane active polymers, however, arepotentially toxic when administered in vivo. Polyamines also interactreadily with many anionic components in vivo, leading to undesiredbio-distribution. Therefore, reversible masking of membrane activity ofthe polyamine is necessary for in vivo use. This masking is accomplishedthrough reversible attachment of masking agents to the membrane activepolyamine to form a reversibly masked membrane active polymer, i.e. adelivery polymer. In addition to inhibiting membrane activity, themasking agents shield the polymer from non-specific interactions, reduceserum interactions, increase circulation time, and provide cell-specificinteractions, i.e. targeting.

Masking agents, in aggregate, may inhibit membrane activity of thepolymer and provide in vivo hepatocyte targeting. Masking agents mayalso shield the polymer from non-specific interactions (reduce seruminteractions, increase circulation time). The membrane active polyamineis membrane active in the unmodified (unmasked) state and not membraneactive (inactivated) in the modified (masked) state. A sufficient numberof masking agents are linked to the polymer to achieve the desired levelof inactivation. The desired level of modification of a polymer byattachment of masking agent(s) is readily determined using appropriatepolymer activity assays. For example, if the polymer possesses membraneactivity in a given assay, a sufficient level of masking agent is linkedto the polymer to achieve the desired level of inhibition of membraneactivity in that assay. Masking requires modification of ≧50%, ≧60%,≧70%, ≧80% or ≧90% of the primary amine groups on a population ofpolymer, as determined by the quantity of primary amines on the polymerin the absence of any masking agents. It is also a preferredcharacteristic of masking agents that their attachment to the polymerreduces positive charge of the polymer, thus forming a more neutraldelivery polymer. It is desirable that the masked polymer retain aqueoussolubility. Masking with PEGs also helps in prevention of aggregation ofelectrically neutral polymers which can result in formation of largeparticles.

As used herein, a membrane active polyamine is masked if the modifiedpolymer does not exhibit membrane activity and exhibits cell-specific(i.e. hepatocyte) targeting in vivo. A membrane active polyamine isreversibly masked if cleavage of bonds linking the masking agents to thepolymer results in restoration of amines on the polymer therebyrestoring membrane activity.

As used herein, a masking agent comprises a disubstituted maleicanhydride compound of the invention having an targeting moiety (orgroup) or a steric stabilizer at position Z. A preferred targetingmoiety is an ASGPr targeting moiety. An ASGPr targeting moiety is agroup, typically a saccharide, having affinity for theasialoglycoprotein receptor. A preferred steric stabilizer is apolyethylene glycol (PEG). The membrane active polyamine can beconjugated to masking agents in the presence of an excess of maskingagents. The excess masking agent may be removed from the conjugateddelivery polymer prior to administration of the delivery polymer.

As used herein, a targeting group is a ligand having affinity for a cellsurface receptor. Targeting moieties or groups enhance thepharmacokinetic or biodistribution properties of a conjugate to whichthey are attached to improve cell-specific distribution andcell-specific uptake of the conjugate. Preferred targeting groupscontain saccharides having affinity for the ASGPr, including but notlimited to: galactose, N-Acetyl-galactosamine and galactose derivatives.Galactose derivatives having affinity for the ASGPr are well known inthe art. A variety of ligands have been used to target drugs and genesto cells and to specific cellular receptors. Cell receptor ligands maybe selected from the group comprising: carbohydrates, glycans,saccharides (including, but not limited to: galactose, galactosederivatives, mannose, and mannose derivatives), vitamins, folate,biotin, aptamers, and peptides (including, but not limited to:RGD-containing peptides, insulin, EGF, and transferrin). Examples oftargeting groups include those that target the asialoglycoproteinreceptor by using asialoglycoproteins or galactose residues. Forexample, liver hepatocytes contain ASGP Receptors. Therefore,galactose-containing targeting groups may be used to target hepatocytes.Galactose containing targeting groups include, but are not limited to:galactose, N-acetylgalactosamine, oligosaccharides, and saccharideclusters (such as: Tyr-Glu-Glu-(aminohexyl GalNAc)₃, lysine-basedgalactose clusters, and cholane-based galactose clusters). Furthersuitable conjugates can include oligosaccharides that can bind tocarbohydrate recognition domains (CRD) found on theasialoglycoprotein-receptor (ASGP-R). Example conjugate moietiescontaining oligosaccharides and/or carbohydrate complexes are providedin U.S. Pat. No. 6,525,031.

Galactose and galactose derivates have been used to target molecules tohepatocytes in vivo through their binding to the asialoglycoproteinreceptor (ASGPr) expressed on the surface of hepatocytes. As usedherein, a ASGPr targeting moiety comprises a galactose and galactosederivative having affinity for the ASGPr equal to or greater than thatof galactose. Binding of galactose targeting moieties to the ASGPr(s)facilitates cell-specific targeting of the delivery polymer tohepatocytes and endocytosis of the delivery polymer into hepatocytes.ASGPr targeting moieties may be selected from the group comprising:lactose, galactose, N-acetylgalactosamine (GalNAc, NAG), galactosamine,N-formylgalactosamine, N-acetylgalactosamine, N-propionylgalactosamine,N-n-butanoylgalactosamine, and N-iso-butanoylgalactosamine (Iobst, S. T.and Drickamer, K. J.B.C. 1996, 271, 6686). ASGPr targeting moieties canbe monomeric (e.g., having a single galactosamine) or multimeric (e.g.,having multiple galactosamines) (Baenziger and Fiete, 1980, Cell, 22,611-620; Connolly et al., 1982, J. Biol. Chem., 257, 939-945).

As used herein, a steric stabilizer is a non-ionic hydrophilic polymer(either natural, synthetic, or non-natural) that prevents or inhibitsintramolecular or intermolecular interactions of a polymer to which itis attached relative to the polymer containing no steric stabilizer. Asteric stabilizer hinders a polymer to which it is attached fromengaging in electrostatic interactions. Electrostatic interaction is thenon-covalent association of two or more substances due to attractiveforces between positive and negative charges. Steric stabilizers caninhibit interaction with blood components and therefore opsonization,phagocytosis, and uptake by the reticuloendothelial system. Stericstabilizers can thus increase circulation time of molecules to whichthey are attached. Steric stabilizers can also inhibit aggregation of apolymer. A preferred steric stabilizer is a polyethylene glycol (PEG) orPEG derivative. As used herein, a preferred PEG can have about 1-500ethylene glycol monomers, 2-20 ethylene glycol monomers, 5-15 ethyleneglycol monomers, or about 10 ethylene glycol monomers. As used herein, apreferred PEG can also have a molecular weight average of about85-20,000 Daltons (Da), about 200-1000 Da, about 200-750 Da, or about550 Da. As used herein, steric stabilizers prevent or inhibitintramolecular or intermolecular interactions of a polymer to which itis attached relative to the polymer containing no steric stabilizer inaqueous solution.

In one embodiment, the membrane active polyamine is reversibly masked byattachment of ASGPr targeting moiety masking agents to ≧50%, ≧60%, ≧70%,≧80%, or ≧90% of primary amines on the polyamine. In another embodiment,the membrane active polyamine is reversibly masked by attachment ofASGPr targeting moiety masking agents and PEG masking agents to ≧50%,≧60%, ≧70%, ≧80%, or ≧90% of primary amines on the polymer. When bothASGPr targeting moiety masking agents and PEG masking agents, a ratio ofPEG to ASGPr targeting moiety is about 0-4:1, more preferably about0.5-2:1.

The term polynucleotide, or nucleic acid or polynucleic acid, is a termof art that refers to a polymer containing at least two nucleotides.Nucleotides are the monomeric units of polynucleotide polymers.Polynucleotides with less than 120 monomeric units are often calledoligonucleotides. Natural nucleic acids have a deoxyribose- orribose-phosphate backbone. A non-natural or synthetic polynucleotide isa polynucleotide that is polymerized in vitro or in a cell free systemand contains the same or similar bases but may contain a backbone of atype other than the natural ribose or deoxyribose-phosphate backbone.Polynucleotides can be synthesized using any known technique in the art.Polynucleotide backbones known in the art include: PNAs (peptide nucleicacids), phosphorothioates, phosphorodiamidates, morpholinos, and othervariants of the phosphate backbone of native nucleic acids. Basesinclude purines and pyrimidines, which further include the naturalcompounds adenine, thymine, guanine, cytosine, uracil, inosine, andnatural analogs. Synthetic derivatives of purines and pyrimidinesinclude, but are not limited to, modifications which place new reactivegroups on the nucleotide such as, but not limited to, amines, alcohols,thiols, carboxylates, and alkylhalides. The term base encompasses any ofthe known base analogs of DNA and RNA. A polynucleotide may containribonucleotides, deoxyribonucleotides, synthetic nucleotides, or anysuitable combination. Polynucleotides may be polymerized in vitro, theymay be recombinant, contain chimeric sequences, or derivatives of thesegroups. A polynucleotide may include a terminal cap moiety at the 5′end, the 3′ end, or both the 5′ and 3′ ends. The cap moiety can be, butis not limited to, an inverted deoxy abasic moiety, an inverted deoxythymidine moiety, a thymidine moiety, or 3′ glyceryl modification.

An RNA interference (RNAi) polynucleotide is a molecule capable ofinducing RNA interference through interaction with the RNA interferencepathway machinery of mammalian cells to degrade or inhibit translationof messenger RNA (mRNA) transcripts of a transgene in a sequencespecific manner. Two primary RNAi polynucleotides are small (or short)interfering RNAs (siRNAs) and micro RNAs (miRNAs). RNAi polynucleotidesmay be selected from the group comprising: siRNA, microRNA,double-strand RNA (dsRNA), short hairpin RNA (shRNA), and expressioncassettes encoding RNA capable of inducing RNA interference. siRNAcomprises a double stranded structure typically containing 15-50 basepairs and preferably 21-25 base pairs and having a nucleotide sequenceidentical (perfectly complementary) or nearly identical (partiallycomplementary) to a coding sequence in an expressed target gene or RNAwithin the cell. An siRNA may have dinucleotide 3′ overhangs. An siRNAmay be composed of two annealed polynucleotides or a singlepolynucleotide that forms a hairpin structure. An siRNA molecule of theinvention comprises a sense region and an antisense region. In oneembodiment, the siRNA of the conjugate is assembled from twooligonucleotide fragments wherein one fragment comprises the nucleotidesequence of the antisense strand of the siRNA molecule and a secondfragment comprises nucleotide sequence of the sense region of the siRNAmolecule. In another embodiment, the sense strand is connected to theantisense strand via a linker molecule, such as a polynucleotide linkeror a non-nucleotide linker. MicroRNAs (miRNAs) are small noncoding RNAgene products about 22 nucleotides long that direct destruction ortranslational repression of their mRNA targets. If the complementaritybetween the miRNA and the target mRNA is partial, translation of thetarget mRNA is repressed. If complementarity is extensive, the targetmRNA is cleaved. For miRNAs, the complex binds to target sites usuallylocated in the 3′ UTR of mRNAs that typically share only partialhomology with the miRNA. A “seed region”—a stretch of about seven (7)consecutive nucleotides on the 5′ end of the miRNA that forms perfectbase pairing with its target—plays a key role in miRNA specificity.Binding of the RISC/miRNA complex to the mRNA can lead to either therepression of protein translation or cleavage and degradation of themRNA. Recent data indicate that mRNA cleavage happens preferentially ifthere is perfect homology along the whole length of the miRNA and itstarget instead of showing perfect base-pairing only in the seed region(Pillai et al. 2007).

Lists of known miRNA sequences can be found in databases maintained byresearch organizations such as Wellcome Trust Sanger Institute, PennCenter for Bioinformatics, Memorial Sloan Kettering Cancer Center, andEuropean Molecule Biology Laboratory, among others. Known effectivesiRNA sequences and cognate binding sites are also well represented inthe relevant literature. RNAi molecules are readily designed andproduced by technologies known in the art. In addition, there arecomputational tools that increase the chance of finding effective andspecific sequence motifs (Pei et al. 2006, Reynolds et al. 2004,Khvorova et al. 2003, Schwarz et al. 2003, Ui-Tei et al. 2004, Heale etal. 2005, Chalk et al. 2004, Amarzguioui et al. 2004).

The term “small molecule” as used herein, refers to organic or inorganicmolecules either synthesized or found in nature, generally having amolecular weight less than 10,000 grams per mole, optionally less than5,000 grams per mole, and optionally less than 2,000 grams per mole.

As used herein, an “aliphatic group” is a univalent group derived froman aliphatic compound by removal of a hydrogen atom from a carbon atom.An aliphatic compound is an acyclic or cyclic, saturated or unsaturatedcarbon compound, excluding aromatic compounds, in which carbon atoms arejoined together in straight chains, branched chains, or non-aromaticrings. Also as used herein, elements other than hydrogen can be bound tothe carbon chain including, but not limited to: oxygen, nitrogen,sulfur, and chlorine.

As used herein, in vivo means that which takes place inside an organismand more specifically to a process performed in or on the living tissueof a whole, living multicellular organism (animal), such as a mammal, asopposed to a partial or dead one.

A conjugate of the present invention can be administered by a variety ofmethods known in the art. As will be appreciated by the skilled artisan,the route and/or mode of administration will vary depending upon thedesired results. To administer a conjugate of the invention by certainroutes of administration, it may be necessary to coat the conjugatewith, or co-administer the conjugate with, a material to prevent itsinactivation. For example, the conjugate may be administered to asubject in an appropriate carrier or a diluent. Pharmaceuticallyacceptable diluents include saline and aqueous buffer solutions.Pharmaceutical carriers include sterile aqueous solutions or dispersionsand sterile powders for the extemporaneous preparation of sterileinjectable solutions or dispersion. The use of such media and agents forpharmaceutically active substances is known in the art.

A carrier may also contain adjuvants such as preservatives, wettingagents, emulsifying agents, and dispersing agents. Prevention of thepresence of microorganisms may be ensured both by sterilizationprocedures, supra, and by the inclusion of various antibacterial andantifungal agents, for example, paraben, chlorobutanol, phenol, sorbicacid, and the like. It may also be desirable to include isotonic agents,such as sugars, sodium chloride, and the like into the compositions. Inaddition, prolonged absorption of the injectable pharmaceutical form maybe brought about by the inclusion of agents which delay absorption suchas aluminum monostearate and gelatin.

In pharmacology and toxicology, a route of administration is the path bywhich a drug, fluid, poison, or other substance is brought into contactwith the body. In general, methods of administering drugs and nucleicacids for treatment of a mammal are well known in the art and can beapplied to administration of the compositions of the invention. Thecompounds of the present invention can be administered via any suitableroute, most preferably parenterally, in a preparation appropriatelytailored to that route. Thus, the compounds of the present invention canbe administered by injection, for example, intravenously,intramuscularly, intracutaneously, subcutaneously, or intraperitoneally.Accordingly, the present invention also provides pharmaceuticalcompositions comprising a pharmaceutically acceptable carrier orexcipient.

The phrases “parenteral administration” and “administered parenterally”as used herein means modes of administration other than enteral andtopical administration, usually by injection, and includes, withoutlimitation: intravascular, intravenous, intraarterial, intramuscular,intraparenchymal, intratumoral, intrathecal, intracapsular,intraorbital, intracardiac, intraperitoneal, transtracheal,subcutaneous, subdermal, subcuticular, intraarticular, subcapsular,subarachnoid, intraspinal, subdural, epidural, intrathecal,intralymphatic, and intrasternal injection and infusion.

Regardless of the route of administration selected, the conjugates ofthe present invention, which may be used in a suitable hydrated form,and/or the pharmaceutical compositions of the present invention, areformulated into pharmaceutically acceptable dosage forms by conventionalmethods known to those of skill in the art.

The described compositions are injected in pharmaceutically acceptablecarrier solutions. Pharmaceutically acceptable refers to thoseproperties and/or substances which are acceptable to the mammal from apharmacological/toxicological point of view. The phrase pharmaceuticallyacceptable refers to molecular entities, compositions, and propertiesthat are physiologically tolerable and do not typically produce anallergic or other untoward or toxic reaction when administered to amammal Preferably, as used herein, the term pharmaceutically acceptablemeans approved by a regulatory agency of the Federal or a stategovernment or listed in the U.S. Pharmacopeia or other generallyrecognized pharmacopeia for use in animals and more particularly inhumans. As used herein, “pharmaceutical composition” includes theconjugates of the invention, a pharmaceutical carrier or diluent and anyother media or agent necessary for formulation. As used herein,“pharmaceutical carrier” includes any and all solvents, dispersionmedia, coatings, antibacterial and antifungal agents, isotonic andabsorption delaying agents, and the like that are physiologicallycompatible. Preferably, the carrier is suitable for intravenous,intramuscular, subcutaneous, parenteral, spinal or epidermaladministration (e.g. by injection or infusion).

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of the present invention may be varied so as to obtain anamount of the active ingredient which is effective to achieve thedesired therapeutic response for a particular patient, composition, andmode of administration, without being toxic to the patient. The selecteddosage level will depend upon a variety of pharmacokinetic factorsincluding the activity of the particular compositions of the presentinvention employed, the route of administration, the time ofadministration, the rate of excretion of the particular compound beingemployed, the duration of the treatment, other drugs, compounds and/ormaterials used in combination with the particular compositions employed,the age, sex, weight, condition, general health and prior medicalhistory of the patient being treated, and like factors well known in themedical arts.

RNAi polynucleotides may be delivered for research purposes or toproduce a change in a cell that is therapeutic. In vivo delivery of RNAipolynucleotides is useful for research reagents and for a variety oftherapeutic, diagnostic, target validation, genomic discovery, geneticengineering, and pharmacogenomic applications. Levels of a reporter(marker) gene expression measured following delivery of a polynucleotideindicate a reasonable expectation of similar levels of gene expressionfollowing delivery of other polynucleotides. Levels of treatmentconsidered beneficial by a person having ordinary skill in the artdiffer from disease to disease. A person having ordinary skill in theart of gene therapy would reasonably anticipate beneficial levels ofexpression of a gene specific for a disease based upon sufficient levelsof marker gene results.

EXAMPLES Example 1 Cyclohexene-CDM (CycHex-CDM) Derivative

A) 1,2,4-tricarboxy-1-cyclohexene 2

1,2,4-tricarbomethoxy-1-cyclohexene 1 (465 mg, 1.8 mmol (Claude et al.,J. Org. Chem. 2004, 69, 757-764)) was refluxed in a mixture of EtOH (10mL) and 2N KOH (4 mL) for 1 h. EtOH was removed by rotary evaporation,The residue was diluted with H₂O (20 mL), washed 3 times with DCM,acidified to pH=1 with 10% HCl and product 2 was extracted with EtOAc.The extract was dried using Na₂SO₄ as a drying agent, concentrated, anddried in vacuo. Yield 296 mg (73%). ¹H-NMR (DMSO-d₆): 1.6-1.64 m (1H);1.87-2.00 m (1H); 2.20-2.40 m (5H); 2.42-2.60 m (1H).

B) CycHex-CDM-Cl 3

Triacid 2 (50 mg, 0.234 mmol) was suspended in dichloroethane (10 mL),treated with oxalyl chloride (0.3 mL, 3.4 mmol), and stirred for 24 h at20° C. All volatiles were removed by rotary evaporation at 25° C. andthe residue was dried in vacuo for 4 h.

C) CycHex-CDM-PEG₁₂ 4

At 0° C., a solution of PEG₁₂ amine (112 mg, 0.2 mmol) and pyridine (92μL, 1.17 mmol) in DCM (3 mL) was added dropwise into a stirredsuspension of CycHex-CDM-Cl 3 (0.234 mmol) in DCM (5 mL). After 20 minat 0° C., the stirring was continued at 20° C. for 16 h. The solvent wasremoved by rotary evaporation and product 4 was purified by HPLC.Column: Gemini (Phenomenex) 5 μm, C-18, 110 Å, 250×21.2 mm. Mobile phaseCH₃CN: H₂O (HCO₂H 0.1%), CH₃CN gradient; 15-35% (30 min) Product wasconcentrated in vacuo, redissolved in H₂O and freeze-dried. Yield 10 mg.MS (ES): 756.5 [M+H]⁺, 773.6 [M+NH₄]⁺.

Example 2 Benzo-CDM Derivatives

A) (5E,7E)-5,7-undecandienoic acid 6

LiBr (1.5 M, 56 mL, 84 mmol) was added to a solution of(4-carboxybutyl)triphenylphosphonium bromide 5 (11.08 g, 25 mmol) in THF(45 mL) and cooled to −75° C. While stirring, PhLi (1.8 M in dibutylether, 31 mL, 55 mmol) was added dropwise, keeping the temperature ofthe reaction mixture between −75° C. and −70° C. The cooling bath wasremoved and the reaction mixture was gradually warmed over 30 min to 25°C. The solution was then cooled to −75° C. and (2E)-2-pentenal (2.103 g,25 mmol) was added via syringe. The reaction mixture was stirred for 5min at −75° C. and PhLi (15 mL, 27 mmol) was added over a period of 30min. The reaction mixture was then stirred for 30 min at −75° C., warmedto 25° C. for 30 min, and then cooled again to −75° C. Hydrogen chloride(1M solution in Et₂O, 28 mL, 28 mmol) was added. After 5 min, t-BuOK(3.36 g, 30 mmol) was added. The reaction mixture was allowed to warm to25° C., stirred for 1 h, and poured into ice cold water (90 mL). Thereaction mixture was concentrated twice by rotary evaporation. Unreactedaldehyde was extracted with Et₂O. The aqueous layer was acidified topH=1 with 20% HCl, the product was extracted with Et₂O, dried (MgSO₄),and purified in a SiO₂ column (Hex:EtOAc:AcOH=8:2:0.05). Yield 1.342 g(32%). ¹H-NMR (CDCl₃): 1.00 t (3H, CH₃); 1.70 m (2H, CH₂); 2.05-2.15 m(4H, 2CH₂); 2.36 t (2H, CH₂); 5.48-5.57 m (1H, CH); 5.60-5.67 m (1H,CH); 5.96-6.06 m (2H, 2CH). MS (ES, Neg); 166.9 [M−1]⁻; 395.6[2M+AcOH−1]⁻.

B) 4-[7-ethyl-4,7,8,9-tetrahydro-benzo[c]firan-1,3-dione]butyric acid 7

A mixture of acid 6 (1.21 g, 7.2 mmol) and maleic anhydride (741 mg,7.56 mmol) in toluene (60 mL) was refluxed for 8 h. The Diels-Alderadduct product was concentrated in vacuo and purified on a SiO₂ column(Hex:EtOAc:AcOH=7:3:0.05). Yield 1.03 g (53%) ¹H-NMR (CDCl₃): 1.08 t,(3H, CH₃); 1.76-1.98 m (6H, 3CH₂); 2.12-2.21 m (1H); 2.24-2.32 m (1H,CH); 2.42-2.52 m (2H, CH₂); 3.36-3.44 m (2H, CH₂); 5.80-5.90 m (2H,2CH). MS (ES, neg): 265.2 [M−1]⁻; 531.4 [2M−1]⁻.

C) 5-(3-Carboxypropyl)-2-ethyl-phthalic anhydride (benzo-CDM) 8

A mixture of adduct 7 (0.5 g, 1.88 mmol) and sulfur (120 mg, 3.76 mmol)in diphenyl ether (3.5 mL) was heated under Argon with stirring on asand bath at 270° C. for 3.5 h. The reaction mixture was cooled andtriturated with hexane. The product was separated by centrifugation andpurified on a SiO₂ column (AcOH. 0.5% solution in CHCl₃). Yield 273 mg(56%): ¹H-NMR (CDCl₃): 1.30 t (3H, CH₃); 1.98-2.06 m (2H, CH₂); 2.45 t(2H, CH₂); 3.07-3.15 m (4H, 2 CH₂); 7.59 s (2H, CH). MS (ES, neg): 261.3[M−1]⁻; 523.6 [2M−1]⁻.

D) Benzo-CDM-NH-PEG-OCH₃ (Benzo-CDM-PEG) 10

Benzo-CDM 8 (56 mg, 0.214 mmol) was suspended in anhydrous DCM (5 mL) bywater bath sonication. Oxalyl chloride (93 μL, 1 mmol) was added,stirred for 20 h, and all volatiles were removed by rotary evaporationat 25° C. The benzo-CDM-COCl 9 was dried in vacuo for 4 h andredissolved in anhydrous DCM (3 mL). CH₃O-PEG₁₂-NH₂ (100 mg, 0.178 mmol)was dried of residual water by addition of anhydrous 1,4-dioxanefollowed by rotary evaporation. Drying by azeotropic distillation wasrepeated 3× and finally high vacuum was applied for 3 h. Dry PEG-aminewas dissolved in anhydrous DCM (2 mL) along with anhydrous pyridine(84.5 μL, 1.07 mmol). This solution was added dropwise into a stirringsolution of benzo-CDM-COCl 9 at 0° C. After 30 min, the cooling bath wasremoved, and the solution was stirred for 8 h at 20° C. Productbenzo-CDM-PEG 10 was concentrated in vacuo and purified on HPLC. ColumnAquasil (Thermo), 5 μm, C-18, 250×21.2 mm. Mobile phase: H₂O—CH₃CN(0.01% TFA) CH₃CN gradient; 30-52%, 35 min. Product was concentrated invacuo, redissolved in H₂O and freeze-dried. Yield 40 mg. ¹H-NMR (CDCl₃):3.30 t (3H, CH₃); 1.95-1.21 m (2H, CH₂); 2.29 t (2H, CH₂CO); 3.06-3.13 m(4H, 2CH₂Ph); 3.39 s (3H, CH₃); 3.42-3.47 m (2H, CH₂); 3.54-3.72 m (46H,PEG); 7.58 d (1H, J=7.9 Hz); 7.62 d (1H, J=7.9 Hz, Ar). MS (ES); 804.6[M+1]⁺; 822.5 [M+H₂O+1]⁺; 288.2 [Benzo-CDM-NH—CH═CH₂+1]⁺.

E) Benzo-CDM-NH-NAG 13

Benzo-CDM 8 (100 mg, 0.38 mmol) was converted into benzo-CDM-COCl 9 asdescribed above, and dissolved in anhydrous DCM (4 mL).Ac₃-NAG-PEG-amine 11 (0.163 mg, 0.347 mmol) was dried of residual waterby addition of anhydrous 1,4-dioxane followed by rotary evaporation.Drying by azeotropic distillation was repeated 3 times, followed bydrying in high vacuum for 3 h. Dry material was dissolved in anhydrousDCM (4 mL) containing anhydrous pyridine (150 μL, 1.9 mmol). Thissolution was added dropwise into a stirring solution of benzo-CDM-COCl 9at 0° C. After 30 min, the cooling bath was removed and the stirring wascontinued for 20 h at 20° C. All volatiles were removed by rotaryevaporation and dried in vacuo. The residue was dissolved in CHCl₃ (75mL), washed with cold 5% HCl, H₂O, and dried with Na₂SO₄. Columnpurification on SiO₂ (CHCl₃:EtOAc:AcOH=4:5:5:0.1) affordedacetyl-protected benzo-CDM-NAG 12, yield 74 mg (31%). The product wasstirred in a mixture of MeOH (3 mL): H₂O (2 mL): Et₃N (2 mL) for 20 h,concentrated in vacuo, redissolved in MeOH (8 mL) and stirred withactivated charcoal (3 mg) for 30 min. Following filtration andconcentration in vacuo, the product, benzo-CDM-NAG 13, was passedthrough a Dowex-50WX8-200 (1.5 mL) column (eluent=MeOH: H₂O=2:1). Thistreatment removed Et₃N from the product and converts it in to anhydrideform due to acidity of released free AcOH. This product was dried invacuo, redissolved in H₂O, and freeze-dried. Yield 40 mg (66%). ¹H-NMR(D₂O, NaHCO₃, pH=8.5, different conformations): 1.12-1.20 m (3H, CH₃);1.80-1.92 m (2H, CH₂); 2.03 and 2.04 2 s (3H, Ac); 2.22-2.32 m (2H,CH₂); 2.60-2.76 (m 4H, 2CH₂-Ph); 3.32-3.41 m (2H, CH₂N); 3.56-4.04 m(12H, NAG-OCH₂CH₂OCH₂); 4.44 and 4.46 2d (1H, C¹—H galactose), 7.10-7.40m (2H, Ar). MS (ES); 553 [M+1]⁺; 585.4 [M+MeOH+1]⁺. MS (ES, neg): 551[M−1]⁻; 569 [M+H₂O−1]⁻; 583 [M+MeOH−1]⁻.

Example 3 (Meta-Ar)-CDM Derivatives

A). Methyl 3-(cyanomethyl)benzoate 15

To a stirring aqueous solution (60 mL) of potassium cyanide (3.62 g,55.7 mmol) at 65° C. was added dropwise methyl 3-(bromomethyl)benzoate14 (10.2 g, 44.5 mmol) in absolute ethanol (50 mL) over a period of 0.5h. After addition, the reaction was stirred for 1.5 h at 65° C. Thesolution was then diluted with absolute ethanol (500 mL), cooled on icebath, filtered, and concentrated with a rotary evaporator. The crude wastreated with chloroform (350 mL), dried over MgSO₄, filtered,concentrated, and used without further purification. Yield 6.3 g (81%).¹H-NMR (CDCl₃): 3.81 br s (2H, CH₂), 3.93 s (3H, CH₃); 7.45-7.51 m (1H,CH), 7.53-7.58 m (1H, CH), 7.99-8.04 m (2H, CH).

B) 3-Carboxymethylbenzoic Acid 16

Methyl 3-(cyanomethyl)benzoate 15 (6.3 g, 36.0 mmol) was treated withH₂SO₄ (40%, 108 mL) and refluxed for 3 h at 160° C. The reaction mixturewas then slowly cooled, diluted with cold H₂O (108 mL), and filtered.The solid collected was washed with cold H₂O, dried with vacuum pump,and used without further purification. Yield 4.4 g (68%). ¹H-NMR (DMSO):3.67 s (2H, CH₂); 7.44 t (1H, CH), 7.51 dt (1H, CH), 7.82 dt (1H, CH),7.85 t (1H, CH).

C) Meta-Ar-CDM-CO₂H 17

A stirring solution of acetic anhydride (66 mL) containing3-carboxymethylbenzoic acid 16 (4.4 g, 24.5 mmol) and potassium pyruvate(3.08 g, 24.5 mmol) was heated at 120° C. for 20 min and thenconcentrated in vacuo. Excess of acetic anhydride was removed bysuccessive evaporation of toluene from the reaction mixture with arotary evaporator (3×50 mL). The crude was treated with THF (36 mL) andH₂O (30 mL), followed by saturation with NaHCO₃, and then stirred at 20°C. for 17 h. The reaction was then diluted with H₂O (66 mL), and THF wasremoved by rotary evaporation. The suspension was washed with DCM (2×50mL), and the aqueous was acidified to a pH of 1 with 1% HCl. The productwas extracted with ethyl acetate (3×200 mL), and the combined organicswere washed with brine (2×75 mL), dried with Na₂SO₄, filtered, andconcentrated. The crude was purified by silica gel flash chromatography.Mobile Phase: Hexanes-Ethyl Acetate (H3CCO₂H 0.5%), 30-70. Yield 2.87 g(51%). ¹H-NMR (DMSO): 2.20 s (3H, CH₃); 7.70 t (1H, CH), 7.87 dt (1H,CH), 8.09 dt (1H, CH), 8.20 t (1H, CH).

D) Meta-Ar-CDM-PEG₁₂ 19

A solution of Meta-Ar 17 (0.25 g, 1.07 mmol) in DCM (30 mL) was treatedwith oxalyl chloride (0.47 mL, 5.35 mmol) and stirred for 17 h at 20° C.The reaction was concentrated and excess oxalyl chloride removed withvacuum pump. To the resulting solid meta-Ar-CDM-COCl 18 was added DCM(25 mL). The solution was cooled to 0° C., treated dropwise with amixture of dry CH₃O-PEG₁₂-NH₂ (0.43 g, 0.76 mmol) and pyridine (0.35 mL,4.28 mmol) in DCM (10 mL), and stirred for 30 min. The ice bath wasremoved and the mixture was allowed to stir for 17 h at 20° C. Thereaction was then concentrated in vacuo, and the crude purified withHPLC. Column: Aquasil (Thermo Scientific) 5 μm, C-18, 100 Å. Mobilephase: H₂O-Acetonitrile (F₃CO₂H 0.01%), Acetonitrile gradient: 33-40%,35 min. The product 19, Meta-Aromatic-CDM-PEG₁₂, collected was thenlyophilized from H₂O. Yield 97.1 mg (17%). ¹H-NMR (CDCl₃): 2.35 s (3H,CH₃); 3.38 s (3H, OCH₃), 3.52-3.73 m (48H, CH₂); 7.60 t (1H, CH), 7.79 d(1H, CH), 7.97 d (1H, CH), 8.13 s (1H, CH). MS (ES): 258.3 [M−517+1],517.4 [M−258+1]⁺; 730.5 [M−44+1]⁺; 774.5 [M+1]⁺; 791.9 [M+18]⁺; 809.7[M+18+18]⁺.

E) Meta-Ar-CDM-NAG 20

A solution of m-ArCDM-OH 17 (0.10 g, 0.43 mmol) in DCM (10 mL) wastreated with oxalyl chloride (0.19 mL, 2.15 mmol), and concentrated to asolid as described in the preparation of 19. To the resulting solid 18was added DCM (10 mL). The suspension was cooled to 0° C., treateddropwise with a mixture of dry Ac₃-NAG-amine 11 (0.19 g, 0.43 mmol) andpyridine (0.14 mL, 1.72 mmol) in DCM (5 mL), and stirred for 30 min. Theice bath was removed and the mixture was allowed to stir for 17 h at 20°C. The reaction was then concentrated on rotary evaporator and rest ofthe solvent removed with vacuum pump. The resulting crude was treatedwith a mixture of methanol (3 mL), H₂O (2 mL), and triethyl amine (2mL). The solution was stirred for 17 h at 20° C., then concentrated withrotary evaporator, and the crude Meta-Ar-CDM-NAG 20 purified with HPLC.Column: Aquasil (Thermo Scientific) 5 μm, C-18, 100 Å. Mobile phase:H₂O-MeOH (NH₄HCO₂ 20 mM), MeOH gradient: 0-10%, 30 min. The solidcollected was then passed through Dowex resin (22 mL, 50 W×8-200) usingH₂O and MeOH as eluent (MeOH gradient: 30-50%). This treatment removedEt₃N from the product and converts it in to anhydride form due toacidity of released free HCO₂H. The product was then lyophilized fromH₂O. Yield 28.3 mg (13%). ¹H-NMR (D₂O, NaHCO₃): 1.75 s (3H, CH₃), 2.01 s(3, CH₃); 3.54-4.04 m (14H), 4.49 d (1H, CH); 7.49 dt (1H, CH), 7.55 t(1H, CH), 7.63 t (1H, CH), 7.73 dt (1H, CH). MS (ES): 318.4 [M−204]⁻;477.4 [M−44−1]⁻; 495.8 [M+18−44−1]⁻; 521.7 [M−1]⁻; 539.5 [M+18−1]⁻;557.4 [M+18+18−1]⁻; 589.5 [M+18+18+32−1]⁻.

Example 4 Methoxy-(MeO)-CDM Derivatives

A) Methyl 3,5-Dicarbomethoxy-2,3-dehydro-2-methoxymethylpentanoate 22

A solution of diisopropyl amine (1.007 g, 10 mmol) in anhydrous THF (40mL) was cooled to −40° C. under Argon. Butyl lithium (BuLi, 1.6 M inhexane, 6.2 mL, 9.92 mmol) was added and the reaction stirred from 15min at −40° C. Trimethyl 3-methoxyl-2-phosphonopropionate 21 (Leonard etal. Synthesis 2000, Vol. 4, 507-509) (2.5 g, 11.06 mmol,) in THF (5 mL)was added dropwise to the obtained lithium diisopropylamide and stirredfor 20 min at −40° C. The formed ylide was treated with a solution ofdimethyl 2-oxogluterate (1.541 g, 8.85 mmol) in THF (5 mL), stirred for20 min at −40° C. The temperature was raised, over 1.5 h, to −25° C. Thereaction was quenched with saturated solution of NH₄Cl (100 mL). Theproduct was extracted 4× with Et₂O, and washed 2× with KHSO₄ (5%), thenbrine. The aqueous layer was extracted once with Et₂O. Combined Et₂Oextracts were dried (Na₂SO₄) and concentrated in vacuo. Product waspurified on SiO₂ column (33% EtOAc in hexane), yield 1.38 g (56%).¹H-NMR (CDCl₃): 2.50 t (2H); 2.75 t (2H); 3.36 s (3H), 3.68 s (CH₃O);3.77 s (CH₃O), 3.78 s (CH₃O); 4.26 s (2H, CH ₂OCH₃) (MS (ES): 297[M+Na]⁺; 275.1 [M+1]⁺; 243.1 [M-CH₃OH+1]⁺.

B) CH₃O-CDM-CO₂H 23

Triester 22 (1.281 g, 5 mmol) was dissolved in EtOH (35 mL), 2N KOH(11.3 mL) was added and the reaction mixture was refluxed for 1 h. Thesolution was diluted with H₂O (15 mL) and EtOH was removed on by rotaryevaporation. The residue was washed 3× times with DCM and acidified topH=1 with 5% HCl. The product was extracted 4× with EtOAc, dried(Na₂SO₄), and concentrated in vacuo. Yield 806 mg (75%). ¹H-NMR (CDCl₃):2.77 t (2H, CH₂); 2.94 t (2H, CH₂), 3.45 s (3H, CH₃); 4.40 s (2H, CH₂).MS (ES, Neg.): 231 [M+18−1]⁻; 199.3 [M-CH₃OH−1]⁻.

C) MeO-CDM-NH-PEG₁₂-OCH₃ 25

Oxalyl chloride (436 μL, 5 mmol) was added into a solution of MeO-CDM 23(212 mg, 1 mmol) in DCM (5 mL) and stirred for 20 h at 20° C. Thesolvent was removed by rotary evaporation at 25° C. and dried undervacuum for 4 h. The resulting MeO-CDM-COCl 24 was dissolved in anhydrousDCM (4 mL) and cooled on an ice bath to 0° C. CH₃O-PEG₁₂-NH₂ (430 mg,0.769 mmol) in toluene was dried by rotary evaporation of toluene (3×10mL). The dried PEG₁₂ was dissolved in DCM (4 mL), pyridine (360 μL, 4.5mmol) was added, and the resulting solution was added dropwise into coldstirring solution of MeO-CDM-COCl 24. After 30 min, the cooling bath wasremoved and the reaction mixture was stirred for 20 h at 20° C. Thesolution was then diluted with DCM (50 mL). Product was washed with 1%HCl, brine, dried (Na₂SO₄) and concentrated in vacuo, and purified onHPLC. Column: Gemini (Phenomenex) 5 μm, C-18, 110 Å, 250×21.2 mm. Mobilephase: H₂O—CH₃CN (HCO₂H 0.1%), CH₃CN gradient: 17-35%, 35 min. Productwas concentrated in vacuo, redissolved in H₂O and freeze-dried. Yield100 mg (18%). ¹H-NMR (CDCl₃): 2.58 t (2H, CH₂), 2.92 t (2H, CH₂); 3.38 s(3H, CH₃O); 3.42 t (2H, CH₂), 3.44 s (3H, CH₃O) 3.52-3.58 m (4H, 2 CH₂);3.60-3.70 m (44H, 22CH₂); 4.39 s (2H, CH₂O), 6.6 s (1H, NH). MS (ES):756.7 [M+1]⁺, 773.4 [M+18]⁺.

D) MeO-CDM-O-PEG₅₅₀-OCH₃

MeO-CDM-CO₂H 23 (200 mg, 0.935 mmol) was converted into MeO-CDM-COCl asdescribed in preparation of 25 and dissolved in 7 mL DCM. MeO-PEG₅₅₀-0H(Sigma, 343 mg, 623 mmol) was dried by rotary evaporation of 1,4-dioxane(3×5 mL). Dry MeO-PEG₅₅₀-0H and pyridine (0.34 mL, 4.2 mmol) weredissolved in anhydrous DCM (5 mL) and added dropwise into a stirringsolution of MeO-CDM-COCl 24 at 0° C. After 30 min, the cooling bath wasremoved and the reaction mixture stirred for 10 h at 20° C. The reactionmixture was diluted with DCM (60 mL) and washed twice with cold 2% HCl.The aqueous layer was washed once with DCM (15 mL). The organic phaseswere combined, washed with cold brine, dried (MgSO₄), filtered, andconcentrated in vacuo. The product was dissolved in EtOAc (2 mL) andadded dropwise into a stirring cold Et₂O (45 mL). The mixture was placedon dry ice for 10 h. The precipitate was separated on a centrifuge whilecold, dissolved in Et₂O (45 mL), and stirred with activated charcoal(100 mg) for 1 h. Following filtration through Celite, the Et₂O solutionof the product was chilled on dry ice for 4 h. The precipitate wascentrifuged when cold, separated from the Et₂O, and redissolved in Et₂O(40 mL). The precipitation was repeated twice, after which the productwas dried in vacuo, then dissolved in H₂O (20 mL), and freeze-dried.Yield 197 mg. ¹H-NMR (CDCl₃); 2.74 t (2H, CH₂); 2.92 t (2H, CH₂); 3.38 s(3H, CH₃O); 3.44 s (3H, CH₃O); 3.50-3.58 s (2H, CH₂); 3.60-3.70 m (54H,27CH₂); 4.12-4.24 t (2H, CH₂, CH₂OCO); 4.40 s (2H, CH₂OCH₃). MS (ES):704.4, 748.9, 792.9, 836.7, 880.5, 925.3, 968.8 [M+1]⁺; 241.2[MeO-CDM-OCHCH₂]⁺.

E) MeO-CDM-NAG 26

MeO-CDM-CO₂H 23 (202 mg, 0.94 mmol) was converted into MeO-CDM-COCl 24as described in preparation of 25. Ac₃-NAG-PEG-NH₂ 11 (402 mg, 0.854mmol) was dried by rotary evaporation of toluene (3×10 mL) and dissolvedin DCM (3 mL). Pyridine was added (334 μL, 4.23 mmol) and the solutionwas added dropwise into a stirring solution of MeO-CDM-COCl 24 in DCM (2mL) at 0° C. Following 20 h of stirring at 20° C., the reaction mixturewas diluted 10× with DCM, washed twice with cold 3% HCl, dried (Na₂SO₄),and concentrated in vacuo. The acetyl-protected product was purified ona SiO₂ column (eluent: CHCl₃:EtOAc:acetone:acetic acid=4:5:5:0.1). Toremove acetyl protective groups from NAG, the product was stirred for 20h in a mixture of Et₃N (4.5 mL), H₂O (6 mL), MeOH (7.5 mL). Activatedcharcoal (50 mg) was added and the mixture stirred for 1 h. The reactionmixture was then filtered through Celite. Following concentration invacuo, the product was passed through a Dowex—50 W×8-200 (4 mL) column(eluent=H₂O). This treatment removed Et₃N from the product and convertsit in to anhydride form due to acidity of released free AcOH. Theproduct was dried in vacuo, redissolved in H₂O, and freeze-dried. ¹H-NMR(D₂O/NaHCO₃, open form): 2.05 s (3H, Ac); 2.35 t (2H, CH₂), 2.62 t (2H,CH₂), 3.35 s (3H, CH₃O); 3.35-3.40 m (2H, CH₂N); 3.6-4.1 m (12H,galactose+3 CH₂); 4.2 s (2H, CH₂OCH₃); 4.5 d (1H, C¹—H galactose). MS(ES): 505.3 [M+1]⁺; 522.7 [M+18]⁺; 204.3 [NAG]⁺.

Example 5 Amido-CDM Derivatives A) Amido-CDM-PEG

Copper Glycinate 27

Copper glycinate 27 was prepared as described (Sato M, et al. Bulletinof the Chemical Society of Japan 1959, Vol. 32, p. 203-204). An aqueoussolution (100 mL) of copper sulfate (7.97 g, 49.9 mmol) and glycine(7.50 g, 99.9 mmol) was treated with sodium hydroxide (3.99 g, 99.9mmol) and stirred for 30 min at 50° C. The solution was then dilutedwith cold ethanol (350 mL) and the product collected by filtration. Theprecipitate was crystallized as fine needles from ethanol (250 mL) inwater (350 mL). Yield 10.78 g (87%).

β-Hydroxy-β-methylaspartic Acid 28

β-Hydroxy-β-methylaspartic Acid 28 was prepared using a modifiedprocedure as described (Benoiton L, et al. Journal of the AmericanChemical Society 1959, Vol. 81, p. 1726-1729). To an aqueous solution ofsodium hydroxide (0.5 N, 12 mL) containing copper glycinate 27 (0.75 g,3.02 mmol) was added a solution of pyruvic acid (0.32 g, 3.63 mmol) inH₂O (2.5 mL) neutralized with sodium bicarbonate (pH 7). The suspensionwas stirred for 3 min at 20° C., and then let to stand for 16 h at 5° C.The resulting suspension was filtered and the filtrate treated withsodium sulfide (0.25 g, 3.18 mmol) in H₂O (50 mL) for 30 min withstirring at 20° C. The black copper salts were removed by filtration,and the solution concentrated in vacuo. The oily crude was passedthrough Dowex 1-Acetate (25 mL, 200-400 mesh) and concentrated as awhite precipitate (eluent: H₂O). The product collected was neutralizedwith sodium bicarbonate (pH 7) in a minimum of H₂O, and loaded ontoDowex 1-Acetate (25 mL, 200-400 mesh). The column was washed with H₂Ountil no more ninhydrin positive material was collected. The resin wasremoved from the column and stirred in 1 N acetic acid until hydrogensulfide ceased to form. This was reloaded into the column and theproduct was flushed using 1 N acetic acid. Yield 0.31 g (63%). ¹H-NMR(D₂O): 1.49 s (3H, CH₃), 1.54 s (3H′, CH₃′); 4.09 s (1H, CH), 4.18 s(1H′, CH′).

β-PEG₁₂-β-methylaspartic Acid 29

A solution containing β-hydroxy-β-methylaspartic acid 28 (95.4 mg, 0.59mmol) and N,N-diisopropylethylamine (0.31 mL, 1.76 mmol) in DMF (4 mL)was treated with NHS-PEG₁₂ (382 mg, 0.56 mmol) and let to stir for 16 hat 20° C. The solution was then concentrated and purified with HPLC, butit may be used without further purification. Column: Gemini (Phenomenex)5 μm, C-18, 110 Å. Mobile phase: H₂O-MeOH (HCO₂H 0.1%), MeOH gradient:36-44%, 35 min. The solution was concentrated and dried using vacuumpump for 24 h. Yield 260 mg (63%). ¹H-NMR (D₂O): 1.36 s (3H, CH₃), 1.48s (3H′, CH₃′); 2.58-2.75 m (2H, CH₂CONH), 3.38 s (3H, OCH₃); 3.60-3.73 m(44H, OCH₂), 2.83 t (2H, OCH₂); 4.67 s (1H′, CH), 4.99 s (1H, CH). MS(ES): 716.5 [M−18]⁺; 734.5 [M+1]⁺; 751.8 [M+18]⁺; 772.3 [M+38]⁺.

Amido-CDM-PEG₁₂ 30

Dry β-PEG₁₂-β-methylaspartic acid 29 (260 mg, 0.35 mmol) was treatedwith acetic anhydride (5 mL) freshly distilled from dry sodium acetateand stirred for 15 min at 100° C. The reaction was immediatelyconcentrated with a rotary evaporator, dried by evaporation of toluenefrom the reaction mixture (3×, 3 mL), and purified by HPLC. Column:Gemini (Phenomenex) 5 μm, C-18, 110 Å. Mobile phase: H₂O-MeOH (HCO₂H0.1%), MeOH gradient: 39-55%, 30 min. The product collected was thenlyophilized from H₂O (0.01% F₃CCO₂H). Yield 73 mg (30%). ¹H-NMR (D₂O):2.25 s (3H, CH₃), 2.73 t (2H, CH₂CONH), 3.38 s (3H, OCH₃); 3.56 m (2H,OCH₂), 3.59-3.70 m (44H, OCH₂); 3.82 s (2H, OCH₂). MS (ES): 698.6[M+1]⁺; 712.6 [M+32-18]⁺; 715.4 [M+18]⁺; 730.5 [M+32]⁺; 733.6[M+18+18]⁺; 747.6 [M+18+32]⁺.

B) Amido-CDM-N-Acetyl-Galactosamine (Amido-CDM-NAG)

N-Acetyl-Galactose-succinate 31

A solution containing N-acetyl-galactose (1.00 g, 2.30 mmol) 11 andsuccinic anhydride (244 mg, 2.41 mmol) in DCM (22 mL) was treated withtriethyl amine (404 μL, 2.9 mmol) and stirred for 1 h at 20° C. Thesolution was concentrated and the product purified by silica gel flashchromatography. Mobile Phase: CHCl₃-MeOH (H₃CCO₂H 1%), 19-1. Yield 1.18g (96%). ¹H-NMR (DMSO): 1.78 s (3H, OAc), 1.89 s (3H, OAc), 1.99 s (3H,OAc), 2.10 s (3H, NHAc); 2.32 t (2H, OCOCH₂), 2.41 t (2H, NHCOCH₂); 3.17m (2H, OCH₂), 3.38 t (2H, NHCOCH₂), 3.45-3.62 m (3H, CH; OCH₂),3.75-3.92 m (2H, OCH₂) 4.02 br s (3H, CH; AcOCH₂); 4.54 d (1H, CH), 4.98dd (1H, CH), 5.21 d (1H, CH); 7.83 d (1H, NH), 7.89 t (1H, NH). MS (ES):330.3 [M−205+1]⁺; 535.5 [M+1]⁺; 552.5 [M+18]⁺.

β-N-Acetyl-Galactose-β-methylaspartic acid 32

Dry N-acetyl-galactose-succinate 31 (715 mg, 1.34 mmol) in DMF (15 mL)was treated with pentafluorophenol (320 mg, 1.74 mmol), then EDC (333mg, 1.74 mmol), and let to stir for 18 h at 20° C. To the solution at 0°C. was then added dropwise a suspension of β-hydroxy-β-methylasparticacid 28 (283 mg, 1.74 mmol) and N,N-diisopropylethylamine (1.16 mL, 6.68mmol) in DMF (20 mL). The solution was let to warm to 20° C., andstirred for 18 h. It was then concentrated on a rotary evaporator andpurified with HPLC. Column: Aquasil (Thermo Scientific) 5 μm, C-18, 100Å. Mobile phase: H₂O-Acetonitrile (HCO₂H 0.1%), Acetonitrile gradient:11-19%, 30 min. Yield 342 mg (38%). ¹H-NMR (DMSO): 1.17 s (3H, CH₃′),1.36 s (3H, CH₃), 1.78 s (3H, OAc), 1.89 s (3H, OAc), 1.99 s (3H, OAc),2.10 s (3H, NHAc); 2.24-2.39 m (4H, CH₂), 3.18 t (2H, CH₂); 3.38 t (2H,CH₂), 3.45-3.63 m (3H, CH; OCH₂), 3.75-3.92 m (2H, OCH₂) 4.03 br s (3H,CH; AcOCH₂); 4.54 d (1H, CH); 4.57 d (1H, CH), 4.89 d 1H, CH′); 4.97 dd(1H, CH), 5.21 d (1H, CH); 7.82 d (1H, NH), 7.87 t (1H, NH). MS (ES):330.3 [M−360+1]⁺; 351.4 [M−360+22]⁺; 690.4 [M+1]⁺; 702.3 [M+22]⁺; 718.4[M+38]⁺.

Amido-CDM-NAG 33

Amido-CDM-NAG was prepared by treatment ofβ-N-Acetyl-Galactose-β-methylaspartic acid 32 (342 mg, 0.50 mmol) withfreshly distilled acetic anhydride (5 mL) as described in thepreparation of 30. The resulting crude was treated with a mixture ofmethanol (7.5 mL), H₂O (6 mL), and triethyl amine (4.5 mL). The solutionwas stirred for 17 h at 20° C., then concentrated with a rotaryevaporator and purified with HPLC. Column: Aquasil (Thermo Scientific) 5μm, C-18, 100 Å. Mobile phase: H₂O-Acetonitrile (F₃CCO₂H 0.01%),Acetonitrile gradient: 5-25%, 35 min. The product collected was thenlyophilized from H₂O (0.01% F₃CCO₂H). Yield 50 mg (19%). ¹H-NMR (D₂O,NaHCO₃): 1.84 s (3H, CH₃), 2.05 s (3H, CH₃); 2.54-2.76 m (4H, CH₂),3.36-3.44 m (2H, CH₂NHCO); 3.59-4.22 m (12H), 4.5 d (1H, CH). MS (ES):204.3 [M−314+1]⁺; 314.9 [M−204+1]⁺; 333.3 [M−204+18]⁺; 347.3[M−204+32]⁺; 518.6 [M+1]⁺; 536.6 [M+18]⁺; 550.6 [M+32]⁺; 572.4[M+32+32]⁺; 588.3 [M+32+38]⁺.

Example 6 Polymer-siRNA Conjugation

A) Modification of Amino-siRNA with Thioacetyl Group

SATA-modified siRNAs were synthesized by reaction of 5′ amine-modifiedsiRNA with 1 weight equivalents (wt. eq.) ofN-succinimidyl-S-acetylthioacetate (SATA) reagent (Pierce) and 0.36 wt.eq. of NaHCO₃ in water at 4° C. for 16 hours. The modified siRNAs werethen precipitated by the addition of 9 volumes of ethanol and incubationat −78° C. for 2 hours. The precipitate was isolated and dissolved in1×siRNA buffer (Dharmacon), and quantified by measuring absorbance atthe 260 nm wavelength.

B. Conjugation of siRNA and Polymer, Followed by Reversible Modificationof Polymer.

Polymer was modified by addition of 1.5 wt % SMPT (Pierce). One hourafter addition of SMPT, the 1×mg of modified polymer was added toisotonic glucose solution. To this solution was added <0.25×mgSATA-modified siRNA. To the solution was then added 14×mg of HEPES freebase followed by a mixture of 2.3×mg NAG-containing CDM derivatives and4.7×mg PEG-modified CDM derivatives. The solution was then incubated 0.5hour at room temperature before injection.

Example 7

Reversible Polymer Modification. Reversible modification/masking ofmembrane active polyamine; i.e., modification of membrane active polymerwith CDM-NAG or a mixture of CDM-NAG plus CDM-PEG. Masking of polymer:To a solution of ×mg membrane active polyamine in isotonic glucose wasadded 14×mg of HEPES free base followed by either 7×mg CDM-NAG or amixture of 2.3×mg CDM-NAG and 4.6×mg CDM-PEG, for a total of 7×disubstituted maleic anhydride masking agent. The solution was thenincubated for at least 30 min at RT prior to animal administration.

Example 8 In Vivo siRNA Delivery

A) Administration of RNAi Polynucleotides In Vivo and Delivery toHepatocytes.

RNAi polynucleotide and masked polymers conjugates were synthesized asdescribed above. Six to eight week old mice (strain C57BL/6 or ICR,˜18-20 g each) were obtained from Harlan Sprague Dawley (IndianapolisInd.). Mice were housed at least 2 days prior to injection. Feeding wasperformed ad libitum with Harlan Teklad Rodent Diet (Harlan, MadisonWis.). Mice were injected with 0.2 mL solution of delivery polymer-siRNAconjugates into the tail vein. The composition was soluble andnonaggregating in physiological conditions. Solutions were injected byinfusion into the tail vein. Injection into other vessels, e.g.retro-orbital injection, were equally effective.

B) Serum ApoB Levels Determination.

Mice were fasted for 4 h (16 h for rats) before serum collection bysubmandibular bleeding. Serum ApoB protein levels were determined bystandard sandwich ELISA methods. Briefly, a polyclonal goat anti-mouseApoB antibody and a rabbit anti-mouse ApoB antibody (BiodesignInternational) were used as capture and detection antibodiesrespectively. An HRP-conjugated goat anti-rabbit IgG antibody (Sigma)was applied afterwards to bind the ApoB/antibody complex. Absorbance oftetramethyl-benzidine (TMB, Sigma) colorimetric development was thenmeasured by a Tecan Safire2 (Austria, Europe) microplate reader at 450nm.

C) Plasma Factor VII (F7) Activity Measurements.

Plasma samples from mice were prepared by collecting blood (9 volumes)by submandibular bleeding into microcentrifuge tubes containing 0.109mol/L sodium citrate anticoagulant (1 volume) following standardprocedures. F7 activity in plasma is measured with a chromogenic methodusing a BIOPHEN VII kit (Hyphen BioMed/Aniara, Mason, Ohio) followingmanufacturer's recommendations. Absorbance of colorimetric developmentwas measured using a Tecan Safire2 microplate reader at 405 nm.

TABLE 1 Knockdown of apoB in vivo following injection ofsiRNA-polymer^(a) conjugate reversibly masked with different CDMderivatives. siRNA dose Polymer dose Relative % CDM derivative (mg/kg)(mg/kg) ApoB ^(b, c) Standard CDM 1 15 96 ± 1 Amido-CDM 1 15 94 ± 1 Metaaryl-CDM 1 15 95 ± 1 ^(a)Polymer used was PBAVE (U.S. Pat. No.7,682,626) ^(b) Percent knockdown relative to control group (n = 3)injected with isotonic glucose solution. ^(c) ICR mice

Example 8

siRNA Delivery by co-injeciton of siRNA-cholesterol conjugate andreversibly modified polyamine. Six to eight week old mice (strainC57BL/6 or ICR, ˜18-20 g each) were obtained from Harlan Sprague Dawley(Indianapolis Ind.). Mice were housed at least 2 days prior toinjection. Feeding was performed ad libitum with Harlan Teklad RodentDiet (Harlan, Madison Wis.). Cholesterol was were covalently linked to3′ or 5′ ends of siRNA molecules using techniques standard in the art.Polyamines were reversibly modified as described above. Mice wereinjected with 0.2 mL solution of delivery polymer and 0.2 mL siRNAconjugates into the tail vein. The composition was soluble andnonaggregating in physiological conditions. Solutions were injected byinfusion into the tail vein. Injection into other vessels, e.g.retro-orbital injection, were equally effective.

TABLE 2 Knockdown of apoB in vivo following injection ofsiRNA-cholesterol conjugate coadministered with reversibly masked withdifferent CDM derivatives. siRNA dose Polymer dose^(a) Relative % CDMderivative (mg/kg) (mg/kg) ApoB ^(b, c) Standard CDM 1 15 62 ± 10methoxy-CDM 1 15 67 ± 13 ^(a)Polymer used was PBAVE. ^(b) Percentknockdown relative to control group (n = 3) injected with isotonicglucose solution. ^(c) ICR mice.

Example 9

Circulation times for polymers modified with anhydride derivative-PEGcompounds. Polyamines were modified with the indicated anhydridederivative-PEG compounds and fluorescently labeled. Following polymermodification, the polymers were injected into mice and the circulationtimes monitored by fluorescence.

Ant-86 poly(acrylate) polyamine was labeled with Cy5 or Cy7. The labeledpolymers were then modified with the indicated anhydridederivative-PEG550 (550 MW PEG) compounds by reaction in HEPES bufferedisotonic glucose at pH7.5 at room temperature for 15-30 min. Theconjugates were injected into ICR mice (100 μg polymer per mouse in avolume of 200 μL). At several time points after delivery, a small amountof blood was obtained from the mice and immediately placed on ice. Theblood samples were subsequently spun in serum separation tubes and theserum transferred to new tubes. The amount of polymer in each sample wasdetermined by measuring the fluorescence intensity of the label in afluorometer (Cy5 at 650 nm, Cy7 at 670 nm). The data for each individualmouse were normalized by dividing each value by the value of the firstdata point (typically collected at 2 min after injection to give ameasure of the injected amount). Each sample was injected in three mice.The following table provides the average data obtained for variousformulations. The data reveal different circulation times for polymersconjugated with different anhydride derivative-PEG compounds.

TABLE 3 In vivo clearance from serum of polymers modified withanhydride-PEG compounds. Relative amount of polymer remaining incirculation anhydride 2 min* 30 min 60 min 120 min 2-propionic-3- 1.000.31 ± 0.18 0.06 ± 0.06 0.03 ± 0.03 methylmaleic anhydride NHS(non-labile 1.00 0.94 ± 0.06 0.71 ± 0.12 0.63 ± 0.10 control)Meta-aryl-CDM 1.00 0.61 ± 0.12 0.29 ± 0.06 0.09 ± 0.03 Amido-CDM 1.000.53 ± 0.14 0.39 ± 0.17 0.40 ± 0.00 *Minutes after injection.

We claim:
 1. An anhydride having the structure:

wherein X is —(CH₂)_(n)—Z, Z is selected from the group consisting of:carboxyl group, ester group, amide group, ether group, tertiary aminegroup, protected amine group, targeting group, and steric stabilizergroup; n is an integer from 0-8; and, R1, R2, and R3 are independentlyselected from hydrogen, aliphatic group, and aromatic group.
 2. Ananhydride having the structure:

wherein X is —(CH₂)_(n)—Z, Z is selected from the group consisting of:carboxyl group, ester group, amide group, ether group, tertiary aminegroup, protected amine group, targeting group, and steric stabilizergroup; n is an integer from 0-8; R1, R2, and R3 are independentlyselected from hydrogen, aliphatic group, and aromatic group; and, m isan integer from 1-8.
 3. An anhydride having the structure:

wherein Y is an aliphatic group, aromatic group, —CH₂—O—R1, or—NH—CO—R1; wherein R1 is an aliphatic group. X is —(CH₂)_(n)—Z,

wherein Z is selected from the group consisting of: carboxyl group,hydroxyl group, ester group, amide group, ether group, tertiary aminegroup, protected amine group, targeting group, and steric stabilizergroup; and n is an integer from 0-8;
 4. The anhydride of claim 3wherein: Y is an aliphatic group or an aromatic group, X is

and Z is selected from the group consisting of: carboxyl group, estergroup, amide group, ether group, tertiary amine group, protected aminegroup, targeting group, and steric stabilizer group.
 5. The anhydride ofclaim 3 wherein: Y is —CH₂—O—R1 or —NH—CO—R1, R1 is an aliphatic group,X is —(CH₂)_(n)—Z, and Z selected from the group consisting of: carboxylgroup, ester group, amide group, ether group, tertiary amine group,protected amine group, targeting group, and steric stabilizer group. 6.The anhydride of claim 3 wherein: Y is an aliphatic group, X is

and Z is selected from the group consisting of: hydroxyl group,targeting group, and steric stabilizer group.
 7. The anhydride of any ofclaims 1-6 wherein the targeting group is an N-acetylgalactosamine. 8.The anhydride of any of claims 1-6 wherein the steric stabilizer is apolyethyleneglycol.